On an ungreased griddle or heavy skillet heated over medium, toast the chiles a few at a time: open chiles flat, lay on the hot surface, press flat for a few seconds with a metal spatula, then flip and toast the other side. Set aside.

In the same griddle/skillet roast the tomatoes and garlic, turning occasionally, until blacked in spots and soft, 10 to 15 minutes. Cool slightly, then peel off garlic and tomato skins.

Heat the oil in an earthenware pot over medium-high. When hot enough to make a drop of the puree sizzle fiercely, add the puree all at once and stir for several minutes as it sears and thickens. Stir in another 2 cups of the broth, partially cover and simmer for 5 minutes. Add the sugar.

3. FINISHING THE DISH

Add the beans and cook uncovered until thick, approximately 20 minutes. The sauce will take on a darker appearance. Add more stock if you like a more stew-like consistency.